[en] The distribution of the tetravalent zirconium between acetylacetone (Hacac) solution in different diluents and buffer solution of Na, H-ClO₄ aqueous solution at different temperature has been studied. The stability constants of the formed complex containing couple molecules of (acac) within liberation of one proton have been calculated and found having small values. The thermodynamic parameters have been calculated and found to have positive enthalpy and free energy. The mixture of chelate-acac with adduct (TOPO) was used in the extracton of Zr(IV). The stability constants were found much more larger than the chelate separately and the reaction for forming the species Zr(acac)₂. TOPO was found endothermic. The study also, contains the effect of diluents on the reaction behaviour and capacity